diff --git a/staging/src/k8s.io/apiserver/pkg/endpoints/filters/impersonation.go b/staging/src/k8s.io/apiserver/pkg/endpoints/filters/impersonation.go
index 4803975a735..a6d293a1590 100644
--- a/staging/src/k8s.io/apiserver/pkg/endpoints/filters/impersonation.go
+++ b/staging/src/k8s.io/apiserver/pkg/endpoints/filters/impersonation.go
@@ -164,7 +164,7 @@ func WithImpersonation(handler http.Handler, a authorizer.Authorizer, s runtime.
 		req = req.WithContext(request.WithUser(ctx, newUser))
 
 		oldUser, _ := request.UserFrom(ctx)
-		httplog.LogOf(req, w).Addf("%v is acting as %v", oldUser, newUser)
+		httplog.LogOf(req, w).Addf("%v is impersonating %v", userString(oldUser), userString(newUser))
 
 		ae := audit.AuditEventFrom(ctx)
 		audit.LogImpersonatedUser(ae, newUser)
@@ -183,6 +183,24 @@ func WithImpersonation(handler http.Handler, a authorizer.Authorizer, s runtime.
 	})
 }
 
+func userString(u user.Info) string {
+	if u == nil {
+		return "<none>"
+	}
+	b := strings.Builder{}
+	if name := u.GetName(); name == "" {
+		b.WriteString("<empty>")
+	} else {
+		b.WriteString(name)
+	}
+	if groups := u.GetGroups(); len(groups) > 0 {
+		b.WriteString("[")
+		b.WriteString(strings.Join(groups, ","))
+		b.WriteString("]")
+	}
+	return b.String()
+}
+
 func unescapeExtraKey(encodedKey string) string {
 	key, err := url.PathUnescape(encodedKey) // Decode %-encoded bytes.
 	if err != nil {
diff --git a/staging/src/k8s.io/apiserver/pkg/server/httplog/httplog.go b/staging/src/k8s.io/apiserver/pkg/server/httplog/httplog.go
index 4d6248f834f..a4b4c5899fd 100644
--- a/staging/src/k8s.io/apiserver/pkg/server/httplog/httplog.go
+++ b/staging/src/k8s.io/apiserver/pkg/server/httplog/httplog.go
@@ -205,7 +205,6 @@ func StatusIsNot(statuses ...int) StacktracePred {
 func (rl *respLogger) Addf(format string, data ...interface{}) {
 	rl.mutex.Lock()
 	defer rl.mutex.Unlock()
-	rl.addedInfo.WriteString("\n")
 	rl.addedInfo.WriteString(fmt.Sprintf(format, data...))
 }